Unreasonable to Assume
by Saucery
Summary: A side-story to 'Reasonable to Assume,' although that series is still continuing! This is basically just a series of scenes from Jar's childhood, following him all the way from his first words to his first crush.
1. Chapter 1

**PLEASE NOTE:**

**This website is now purging stories that have mature content.**

**Should my stories be purged, ****you can find my work on AO3 (ArchiveOfOurOwn DOT org) under the same username.**

**Alternatively, you can find me on Twitter as TheSaucery, on Tumblr as SauceFactory ****or on LiveJournal as Saucery.**

**Thank you!**

* * *

**UNREASONABLE TO ASSUME**

**- A sequel to _Reasonable to Assume_ -**

* * *

Stiles struggles to open a bottle of mulch one-handed while also trying to hang onto his mobile phone. It's an acrobatic act worthy of a circus. The Hale Circus. Which, well, that's what it _is_, isn't it? A bunch of dangerous beasts and their unsuspecting ringmaster, Stiles.

The phone almost slips, and Stiles scrabbles with it. Jackson keeps on ranting at the other end.

"Whoa, man, ease up, I can't - no, if you'd only let Lydia - "

Jackson hangs up.

Stiles curses. Jackson's become even more of a bitch after becoming, uh, Lydia's bitch. Not that the word's very politically correct, given that it automatically assumes the preexistence of a binary construct that makes the female inferior to the male (Allison's brain-washing him, she's _evil_), but still. If Jackson keeps scent-marking Lydia _in public_, it's no wonder he ends up with claw-marks across his face. Good thing werewolves heal quickly.

There's a soft shuffle, and Stiles turns from the kitchen counter to see… Jar. Doing that half-crawl, half-wriggle thing toward him. Jar's moved on from the incredibly cute (but developmentally worrying, until Stiles read on an online mothers' forum that it was okay) butt-drag, so Stiles tries to encourage him to crawl. Jar's only eight months old, but he's already got Derek's tendency to creep up on Stiles silently and _stare_ at him.

Like he's doing right now.

"Hey, babe," Stiles smiles, instantly putting Jackson's many idiocies out of his mind. It ain't that difficult, with an adorable were-cherub of his very own. "I bet you want your mulch, huh? Your yummy mulch! It's the yummiest mulch that ever mulched, uh-huh. And guess what, it's beef-mulch! Your favoritest mulch of all!"

Jar claps his hands.

"Gotcha. Now, I'm just gonna… figure out how to open this thing… a-ha! Done!" Now that he isn't juggling multiple uncooperative, inanimate objects, he can get the goddamn bottle to open. And Derek calls him uncoordinated. Pshaw.

The lid pops right off, surprisingly loud, and Jar lets out a happy squeal.

"_That's_ what I like to hear. Eager-beaver babies makin' eager-beaver sounds! You remember that beaver? From the cartoon? With the teeeeeeeeeth?"

Jar wiggles on his bottom. Must be real comfortable, wiggling around on a padded diaper. Like livin' on a mattress. _Way_ better than livin' on a prayer. (Great. Derek's taste for classic rock has already infiltrated Stiles's music references. Soon, Stiles will lose any ability to casually refer to contemporary pop culture. Or quote Ke$ha songs. Stiles has been _cursed_. Cursed with the soundtrack of epic man-pain.)

"You know who else has teeth? Your dad. Your scowly, broody, teethy dad."

"Da."

"Yeah, that's - wait, _what_?"

Jar just blinks huge green eyes at him, totally innocent, unknowing as an angel. A bit of drool escapes his mouth.

"Just - say that again. Did you - did you actually _say_ that? Do mine ears deceive me, or was my darling _talking_? Were you talking to me, baby? You were, weren't you? Because you're a smart kid. Seeing as how you've taken after me. Not after your unimaginative, strong-silent-type of a weredad."

Jar gurgles.

"Dad," says Stiles, because, hey, kids copy their parents, right? "Here a dad. There a dad. Everywhere a dad-dad. Old McDonald had a dad, ee-i, ee-i-oh."

"Dah," Jar says, and Stiles's heart _thumps_. His legs stop supporting him. He literally has to leave the bottle on the counter and sit down on his ass. On the _floor_. Thankfully, that brings him nearly to eye-level with Jar, who's still looking at Stiles like he has no clue why Stiles is freaking out.

"Ohgod," says Stiles. His knees wobble, which is ridiculous, because he's _sitting down_. His heart won't stop hammering. "So this is what they mean when they say kids grow up too fast. You're talking. You're already _talking_. Next thing I know, you'll be giving your graduation speech as the valedictorian of your school - because obviously you'll be the valedictorian of your school - and I'll be trying manfully not to cry into my sleeve. Derek will be filming the whole thing because my hands will be shaking too hard to hold the camera. I can see it happening. Ohgodoh_god_."

Jar makes a quizzical face that, on top of his newfound superpower of word-making, is almost enough to _slay_ Stiles with its perfection.

"And one day, you're gonna bring someone home. And Derek will either castrate them - if they're a guy - or hide up in the attic in a not-terrified-at-all manner if they're a girl. Because Derek can't deal with girls. Just look at how he fails to deal with Lydia. And you'll be like, 'Don't be such a sourwolf,' see, 'cause you'll have learned that from me, my special gift to you, and I'll be like, 'Right on, brother.' Son. Oh, crap, I have a _son_. I'm old by default. Victorian, almost. No wonder I can't quote Ke$ha songs. Egads! Confound it!"

There's a concerned little frown-line on Jar's forehead that looks alarmingly like Derek's.

"No. Do not. Do _not_ with the were-Bambi eyes. You're ridiculously cute. You kill me with cute. Jesus. My heart's still racing. Your voice is beautiful. For all that is holy, please talk again. Please talk _forever_. Your voice is literally the light that, like a sunburst, through yonder window breaks. It's just. It's so _soft_, so… like it has baby-fur, _too_…"

"Duh-da," says Jar.

"That's right. Duh Dad. I'm your Duh Dad. D'oh Dad, even. I'm Homer Simpson. Derek is Marge. But without the girl-parts. Or the giant blue hair. Or the… wow. _Wow_. You're _talking_." Stiles thrills, head to toe, and sweeps Jar up in his arms, laughing.

Jar giggles, drool dripping down his chin. His furry feet kick in their claw-proof socks. (Basically just two extra socks, and they're not really claw-proof, since they already have tiny holes in them. But, whatever.)

The front door swings open.

"Stiles!" Derek yells, _leaping_ into the kitchen like it's the apocalypse, teeth bared. Angry beaver, indeed. "What - " And then, he sees Stiles sprawling on the floor with Jar, both wearing equally dopey grins, and wavers, doubt flickering across his expression. "What happened?"

"What are you _doing_ here? Weren't you going to town?"

"I came back."

"But you must've already reached, right? You left twenty minutes ago. How'd you get all the way back - "

"I _ran_."

"You mean, you bounded. Like a wolf." Stiles sits up. Jar's doing his anxious frown, so Stiles pats his back to calm him. "Why?"

"I heard your heart-rate."

Stiles goggles. "From a _mile_ away? How is that even… Scott can't do that!"

"Scott isn't an Alpha. And you," Derek says, eyes narrowing, "are not his mate."

"Thank god. Allison should be canonized as a saint for putting up with him, seriously."

Derek's glowering. He's definitely glowering. "What made you do that?"

"Do what?" Stiles jiggles Jar on his knee; Jar coos. And tries to lick his neck.

Derek's eyes narrow even _further_. "He's marking you."

"What?"

"Why is he marking you?"

"I don't kn-… oh. My. Gosh. Are you jealous? Are you jealous of a _kid_? I can't believe - "

"Your heart-rate, Stiles. What made it go up?"

"Oh, yeah!" Stiles brightens, because this is the best news _ever_, and he gets to give it. "He talked!"

"Who talked?"

"Jar, who else?"

"He can't talk," Derek scoffs. _Scoffs_, like -

"Are you questioning your own child's intelligence? Because that's bad form. Very, very bad form. For which I might have to kick your ass."

Derek raises an eyebrow.

"Metaphorically," Stiles amends. "I might have to kick your ass _metaphorically_. And he did talk, Cynic Who Knows the Price of Everything but the Value of Nothing."

"Quoting Oscar Wilde won't make your argument any more convincing."

"Proving that you _read_ doesn't make your argument any more convincing, either, _Conan_."

"Conan."

"The barbarian. Not the stand-up comedian."

"I know."

"Do you? Color me shocked."

They glare at each other.

"And anyway, Jar can absolutely prove you wrong. Because Jar's on my side."

"The parenting guide said you shouldn't force your kids to pick sides," Derek says, and Stiles is so secretly delighted that Derek's_reading_ those parenting pamphlets that he almost doesn't snark back.

Almost. "I'm not forcing him. He's _choosing_ the right side. Which I happen to be on. Go ahead, Jar. Launch into your valedictorian speech!"

"His what?"

"You won't understand. You weren't here to witness his miracle of miraculousness." Stiles looks expectantly at Jar. "How 'bout a repeat performance, buddy?"

But Jar… doesn't say anything. He just licks Stiles. Again.

"Even he was startled by your heart-rate. He keeps marking you to protect you from intruders."

"He's such a sweetheart!"

"I _ran back from town_ to protect you from intruders."

"Again, competing with a baby is kind of pathetic, Derek. And it's not my fault you wrecked your Camaro during a 'training exercise' last week and had to run like freakin' Rambo through the forest."

"He still isn't saying anything."

"That's because he needs a warm-up! Okay, Jar," says Stiles, projecting SRS BZNS, and sure enough, Jar focuses on him. "I'm a man-dad. Derek's a weredad. A dad that's glad and a sad, mad dad."

"You've got all the mad, here."

"Mad dad. Dad mad. Bad mad dad."

"Da-da," says Jar, and Derek _freezes_.

"Yes!" Stiles smirks triumphantly up at Derek. "Hear that, Derek?"

Jar grins up at Derek, as well. "De."

"That… _whoa_. That's. That's 'Derek', right? He just said your _name_!"

Derek seems mesmerized. Wide-eyed and mesmerized and sort of concussed, like someone's brained him with a blunt object. His voice, when he speaks, is raspy. "He's… just mimicking sounds. He doesn't know what he's saying."

"Are you a wet blanket reincarnated as a sentient being? Or were you once a box of tissues left out in the rain? Did you melt away into the nothingness of eternal, soggy sorrow? Is that why you're so utterly devoid of hope? C'mon, tell me. I'm _dying_ to know."

Derek reaches down to pet Jar's head, with the sort of awkward-but-extreme gentleness that makes Stiles's breath stutter, whenever he sees it. The way Jar now nuzzles against Derek's palm, instead of shying away from him, does things to Stiles, too.

Stiles clears his throat. "Um, so. He… he's learning how to talk."

"Yes," murmurs Derek, quietly. He still hasn't snapped out of that brained-by-a-blunt-object state, and he's gazing at Jar like - like Jar's doing something amazing, which, heh, Jar _is_. And Derek _does_ think so, no matter what he says.

"You've gotta encourage the kid, you know. Positive reinforcement. It's in the pamphlets."

"I know it's in the pamphlets," Derek growls, and pauses. Eventually, after an infinity of more awkward petting, he says: "Nice job, Jar."

Jar gurgles. And slobbers all over Derek's hand.

Derek… slowly pulls his hand back. And goes to wash it at the sink.

"Right, so I was thinking." Stiles gets up, slinging Jar across his hip. "About college."

Derek turns to look at him. He's still got that weirdly mild aura, like he's been smoking the good stuff. Even his eyebrows aren't making death-threats. "You're not going to college for another year."

"I'm not _going_ anywhere, I'm studying right here. I thought we covered that."

"It's better for you to - "

"Stop it. I'm not leaving Jar. _Or_ you. And I'm gonna be a cop. Not like I need to study at Harvard."

"You could get into Harvard."

"Yeah, well, unlike Lydia, _I don't want to_. It's not my college I'm talking about, anyway."

"Whose - " Derek's eyes flick to Jar. "You can't be serious."

"I'm just sayin'. As soon as I start working, maybe we can start saving up for - "

"Jar's _college_?"

"Hey, my mom and dad started my college fund as soon as I was born. Jar's already _been_ born! He's fallen behind!"

"By eight months."

"I mean, can't you see he's destined to do a Ph.D in Linguistics?"

Derek stares.

"Just look at him. Practically winning intergalactic spelling bees at the tender age of 0.667."

"You may be blowing this out of proportion," Derek drawls, leaning back against the counter. He's got that smirk-not-smirk going on. And that stupid, ruggedly handsome jawline. "Just a bit."

"Ha, ha, ha. No. I'm not. We have to be _prepared_. For anything. So, whaddaya say we start a college fund? And once I start earning - "

"Don't worry about it."

"But - "

"It's covered."

"How - "

"It's. Covered," Derek enunciates, clearly, and steps right into Stiles's space. Not that Stiles _has_ a space, anymore. "There's a trust fund."

"A." Stiles's jaw struggles not to drop to the floor. And fails. Spectacularly. "A _what_?"

"The Hale family set up a trust fund. A long time ago."

"How long?"

"Eighteen years."

"Eigh… teen. _Years_."

Derek just tilts his head. And studies Stiles's neck, where Jar had licked it.

"That's longer than I've been _alive_."

"You're getting better and better at math."

"Shut up," says Stiles, incredulous that Derek didn't tell him about this. Stiles knew about the random investments, but - a trust fund? "It must've built up a hell of a lot of interest, by now."

"Probably."

"_Probably?_"

Derek shrugs. "I haven't checked."

"Okay, that does it. I'm taking over the accounts. Because, even though we're living in the woods, we're not literally _living off berries_, Derek."

"Or rabbits."

"Or rabbits, Jesus _Christ_. How could you even - "

"You don't have to worry about Jar," Derek says, and Stiles… takes a deep breath.

A knot unties itself in his chest. "Yeah," he replies, and thinks of his own parents, all those years ago, saving pennies. "Yeah, all right."

"Mm."

That's the signal that Derek's about to start scenting him. Derek goes non-verbal whenever he has to do that, and he _will_ do that, even if it means putting Jar's feeding-time off by another ten minutes.

So Stiles sighs, and arranges Jar in a way that allows Derek to wrap himself around them.

Which he does.

Soon, Jar starts making this mrr-sound, a sound that takes Stiles a couple of moments to identify as a baby version of Derek's scent-marking purr.

Jesus.

Who's Stiles kidding? Jar's taking after _Derek_.

As that mini-purr mingles with Derek's and vibrates between them, though, Stiles warms right up, from the inside out, and finds that he doesn't mind.

At all.

* * *

Three months later, Stiles has evolved to "Ti," and sometimes, "Ti-Da." Derek is either "Der-Der" or "Der-Da".

Take that, Mr. Wet Blanket.

Also, the trust fund is _massive_. Massive enough to send Jar to Oxford or Princeton or Juilliard, with enough left over for a few thousand NASA space-camps.

Heh.


	2. Chapter 2

**PLEASE NOTE:**

**This website is now purging stories that have mature content.**

**Should my stories be purged, ****you can find my work on AO3 (ArchiveOfOurOwn DOT org) under the same username.**

**Alternatively, you can find me on Twitter as TheSaucery, on Tumblr as SauceFactory ****or on LiveJournal as Saucery.**

**Thank you!**

* * *

**UNREASONABLE TO ASSUME**

**- II -**

* * *

Derek wakes up with the gone-scent of Stiles's skin around him, pressed into the sheets, even though Stiles is no longer here. ("Gotta head back, Derek. Family night, y'know?") Family night. Stiles and his father. ("Be back tomorrow.") Which means today.

His claws sharpen as he runs them over the bed, as if that'll pull Stiles's scent closer to the surface, somehow, instead of this distant sweet-warm thing, lingering like a taste in the back of his throat.

"Grr," says Jar, from the crib on the other side of the room. He's been awake for a while, now, all rustling movements and subvocal growls, obviously restless with Stiles gone.

So they have this in common.

Derek rolls out of bed, drops into a couple of push-ups to get his blood flowing, and then rolls face-up again, into a set of crunches that start a pleasant ache in his abdomen - an ache too swift to fade, thanks to his being what he is.

There's no voice snarking at him or calling him 'Rambo,' no slowly-heating scent of arousal that simmers and shimmers in the thickening air.

Stiles likes watching him work out. Stiles likes -

- spending time with his father.

Not in the same way, of course, but the sheriff really should be accepted into the pack. Officially. Because then, maybe Derek will stop feeling so illogically _betrayed_, as though Stiles still belongs to another pack, still needs -

"Grr-rrr-rr," says Jar, at length, apparently sharing Derek's sentiments. "Ti."

"Stiles isn't here," Derek grunts as he finishes his workout and pads over to the crib. He looks down at Jar, hair sleep-tousled and fur rubbed the wrong way along his arms and legs, because he's been tossing and turning so much. The kid's a calm sleeper, usually. But usually, Stiles is here.

"Dah," Jar scowls, as if seeing Derek first thing in the morning is a massive disappointment. It's no secret who Jar's preferred parent is.

"Yeah, well, I prefer him, too," Derek snaps, nettled, and then wonders if he should feel guilty for saying that to a baby.

Too bad. He doesn't feel guilty, at all.

Jar narrows his eyes in a startlingly perceptive expression, and sinks his half-grown fangs into the plush orange dinosaur that doubles as his chew-toy and 'sleep buddy'. (Stiles's phrase.)

"You'll take its head off," Derek cautions, but Jar just shoots him this rebellious look that doesn't bode well for his teenage years, and keeps on chewing Blahney. (Again, Stiles's name.)

Derek has no idea where the angelic werepup goes to, when Stiles isn't around. Is it possible for babies to have split personalities? None of Stiles's parenting guides seem to think so. There's some stuff in there about 'mirroring' that Stiles pointedly talks about, but Stiles doesn't know anything. Except perhaps everything. It's a phenomenon that Derek is determined to ignore.

The mobile phone chimes on the dresser. It's Stiles, with a text that reads: _Changing time!_

_I know,_ Derek replies, and shoves the phone into his back pocket. The stench of urine through cotton-and-polyester tells him it's changing time a hell of a lot more clearly than anything Stiles could ever say.

Jar gazes up at him expectantly, wriggling back and forth on his mattress while methodically beheading Blahney. His eyes are getting dangerously wet, which means he _also_ knows it's changing time, and if he isn't changed quickly enough, he's going to lodge a complaint about it. Loudly.

Derek takes a deep breath - correction, he _aborts_ a deep breath - and lifts the kid out of his crib.

Jar _yowls_. Right in Derek's _ear_. The sound goes straight through Derek's skull like a spear, and Derek staggers slightly on his way to the changing-table.

Great. None of the others are here, either, for him to pawn this off on. Lydia's always hanging around, these days, because she's stopped pretending not to be a genius and has graduated early, and is basically just waiting for her acceptance letters (_gushing invitations_, she insists) from every single college in the Ivy League, but she's in LA for some sort of Physics conference, this week.

Scott and Jackson are at school. Like Stiles.

So it's just Derek and Jar.

And changing time.

* * *

The day passes with more diaper changes and multiple rounds of pulpy food, with completely superfluous text messages from Stiles, checking up on everything, like Derek isn't the Alpha of an entire pack but a desperately incompetent nanny.

"He's fine," Derek growls, when Stiles finally breaks down and calls at noon. "He's done eating."

Jar perks up at the sound of Stiles's voice, ears flicking up as he makes grabbing motions toward the phone.

Derek ignores him.

"Was it the chicken? Tell me it was the chicken."

"The chicken. With the vegetables."

"How much did he spit back out?"

"What, are you looking for percentages?"

"Yeah, I'm looking for percentages, Einstein. How. Much?"

"The full-stops don't work when you do them."

"The full-stops of menace totally work when I do them, because you're going to tell me how. Much. He. Spit. Out."

"Most of it."

"Most, as in, fifty-five percent? Or seventy-five percent?"

This is getting ridiculous. "Closer to seventy-five."

"Oh, shi - uh. I can't swear where he can hear me, right? And he _can_ hear me."

"He wants the phone."

"What're you waiting for, then? Give him the phone."

"Stiles - "

"Derek. I want to talk to him."

"He'll start crying when you hang up."

"Cra - bs."

"Crabs?" Derek can't help the twitch at the corner of is mouth. "Is there something I should know about, Stiles?"

Stiles chokes. "N-no. I just - I didn't want to swear in front of - "

"Ti!" Jar's face is flushed with agitation. Shit. He's going to start crying. "Ti-Da!'

"Fine, here, take it," Derek says, not at all hurriedly - an Alpha hurrying at the behest of an _infant_ would be insane - and hands the phone over to Jar.

Who snatches at it and immediately starts babbling, consonants and vowels and semi-purrs running together in an incomprehensible blur. The _need_ in them isn't incomprehensible, though.

"Hi, sugar-rush. You doin' fine?" Stiles's voice softens, and it only softens that way with _Derek_ when Stiles has had an orgasm or has just woken up in the mornings. "You gotta eat, sweetheart. Don't want Daddy to worry about you, do you?"

"Dah!"

"That's right. Derek isn't being mean to you, is he?"

"Hey!" Derek yanks the phone back, and Jar hiccups a sob.

"Derek!"

"You're going to have to hang up soon, anyway. You've got class."

"Give it back to him."

"But - "

"Give. It. _Back_."

Derek gives it back.

And paces, uselessly, as Stiles talks to _Jar_ when he could be talking to -

"Okay, Jar, I have to go," says Stiles, at last. "Give the phone back to Derek?"

Derek pounces at it - and the ensuing struggle with Jar is one for the history books, not because of the epic bloodshed, but because it's the only battle Derek has ever fought that doesn't permit him to use brute strength. In the end, he only manages to get the phone after Jar's claws have taken out a button. Another button.

"Which one was it, this time?" Stiles sighs, when Derek secures the phone and leaves Jar blubbering helplessly in the background, eyes glowing green and fangs out.

"The 9."

"So your phone no longer has a 4 or a 9."

Derek shrugs. "I'll get another phone."

"Damn. That's, like, the third phone."

"It's the one baby," Derek points out, and there's a brief silence from the other end.

"I love you," Stiles says, in that way he has of launching completely _devastating_ emotional ambushes.

"I." Derek's skin is suddenly several degrees hotter than it was before. His heart-rate picks up; smells and sounds become sharper. He swears he can _feel_ the shape of Stiles's body on the other end of the line, just by the way the air moves around it. He can _hear_ the air moving around it. "That."

"Ha! Did I give you another feedback loop, Derek-droid? Sorry." Then, there's the click of heeled shoes, and Stiles says: "Whoops, see ya later! Mrs. Gershwin's just about ready to blow a fuse."

And he hangs up.

Derek stands there, stock-still, literally unable to let go of the phone.

The light's painfully bright. He has to wait for his pupils to return to their normal, non-dilated size. When they do, he blinks and returns the phone to his pocket. He notices how quiet it is; Jar's stopped crying, and is instead staring at Derek, transfixed, eyes wide with wonder.

Tear-tracks are still glistening on his face, though, so Derek wipes them away before slinging Jar over his shoulder.

"He just doesn't understand, does he?" Derek murmurs. "He can't understand."

"Mrrr," Jar agrees, just as hushed.

Derek carries him into the bathroom for his bath. Instead of using the baby-bath, Derek gets into the tub himself, after filling it up with warm water and leaving his clothes on the floor. Jar huddles against his chest, head against Derek's shoulder and bottom held carefully in Derek's palm, making cooing noises into Derek's neck.

Looks like the plan's working; the bath's distracted Jar from Stiles's absence, at least for the time being.

Derek's eyelids grow heavy in the warmth, fingers stroking idly through Jar's fur. It waves in the water, velvet-thick and smooth. Jar's feet make occasional, playful splashes, but eventually, they settle down, too.

Jar's falling asleep. His pulse is slowing to match Derek's. His toes curl and uncurl lazily, causing little ripples in the water.

Another three hours before school's out. Derek will do the usual, until then - go online to check on the Hale stocks, contact his broker in New York, shuffle his funds away from the sinkhole that is currently Silicon Valley and keep an eye on Jar, heating up the pureed lamb for Jar's next meal. (It's in the chart Stiles has printed out and stuck to the fridge with a banana-shaped magnet, detailing every meal and its nutritional value. The lamb's good for iron.) He goes over graphs and figures in his head, keeping his fingers moving on Jar, lulling him deeper into sleep.

Derek will climb out of the bath before it gets too cold for Jar, but there's no harm in staying here for a while longer, burying his nose in Jar's wet hair, surrounding himself in Stiles's scent, because Jar always smells like Stiles.

Always.


End file.
